xXDavidCXx
Autocross Champion
- Location
- AZ
- Car(s)
- 2017 GTI SE DSG
Based on my experience in the last two years autocrossing with different setups, and much discussion and disagreement on these forums I've decided to make a concerted effort to model the Mk7 GTI suspension so that we can have concrete evidence for the choices we make.
Caveat: Only a few of these measurements are correct so If anyone has bits of the front suspension lying around, please speak up so we can make this model more accurate.
One of the questions I want to solve is how much body roll results in zero camber on the outside wheel. Any more body roll will result in less contact patch and thus less grip. This might feel like good grip on turn-in, then as the body reaches maximum roll, less grip or understeer.
I've definitely experienced this, but was never sure exactly why.
One reason is not enough tire pressure to support the weight transfer to the front tires. I used to race between 30-35 psi hot, but later in the year, started at 36 and at some event was running 38-40 hot and had much better grip, but still understeered more than I'd like.
The other reason could be that the body roll was putting the outside tire into positive camber. If this is indeed the case, and I'm not willing to compromise ride comfort with more front and rear spring, then a stiffer front bar is required.
Here is where the idea that a larger front swaybar can be beneficial for increased grip, by keeping the roll under -3.3 degrees in this example.
Tire contact patch is depicted by the blue and black bars under each tire.
EDIT: Moved to a pay program for more functionality.
Here is the free racing aspirations suspension to play with. Most measurements are accurate-ish.
Using my winter 225/45/17 wheels and tires.
https://www.racingaspirations.com/mods/zbvcdta5/
x degrees of body roll with x static negative camber when the tire will have zero camber. This is the amount of body roll we need to stop by or before to maximize traction.
1.2 = -1
1.8 = -1.5
2.4 = -2.0
3.0 = -2.5
3.5 = -3.0
Caveat: Only a few of these measurements are correct so If anyone has bits of the front suspension lying around, please speak up so we can make this model more accurate.
One of the questions I want to solve is how much body roll results in zero camber on the outside wheel. Any more body roll will result in less contact patch and thus less grip. This might feel like good grip on turn-in, then as the body reaches maximum roll, less grip or understeer.
I've definitely experienced this, but was never sure exactly why.
One reason is not enough tire pressure to support the weight transfer to the front tires. I used to race between 30-35 psi hot, but later in the year, started at 36 and at some event was running 38-40 hot and had much better grip, but still understeered more than I'd like.
The other reason could be that the body roll was putting the outside tire into positive camber. If this is indeed the case, and I'm not willing to compromise ride comfort with more front and rear spring, then a stiffer front bar is required.
Here is where the idea that a larger front swaybar can be beneficial for increased grip, by keeping the roll under -3.3 degrees in this example.
Tire contact patch is depicted by the blue and black bars under each tire.
EDIT: Moved to a pay program for more functionality.
Here is the free racing aspirations suspension to play with. Most measurements are accurate-ish.
Using my winter 225/45/17 wheels and tires.
https://www.racingaspirations.com/mods/zbvcdta5/
x degrees of body roll with x static negative camber when the tire will have zero camber. This is the amount of body roll we need to stop by or before to maximize traction.
1.2 = -1
1.8 = -1.5
2.4 = -2.0
3.0 = -2.5
3.5 = -3.0
Attachments
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1607479951878.png
Last edited:
